Due to advancements made in telecommunications and data transmissions speeds over unshielded twisted wire pair cables, the connectors (such as jacks and plugs) have become critical impediments to high performance data transmission at high frequencies. Some performance characteristics, particularly due to near end crosstalk, degrade beyond acceptable levels at the higher frequencies, particularly for category 5 and category 6 environments.
When electrical signals are carried on a signal line or wire which is in close proximity to another signal line or other signal lines, energy from one signal can be coupled onto adjacent signal lines by means of the electric field generated by the potential between the two signal lines and the magnetic field generated as a result of the changing electric fields. This coupling, whether capacitive or inductive is called crosstalk, when the coupling occurs between two or more signal lines.
Crosstalk is a noise signal and degrades the signal-to-noise margin (s/n) of a system. In communications systems, reduced s/n margin results in greater error rates in the information conveyed on the signal lines.
One way to overcome this crosstalk problem is to increase the spacing between the signal lines. Another method that can be used is to shield the individual signal lines. However, in many cases, the wiring is pre-existing and standards define geometries and pin definitions for connectors making the necessary changes to such systems cost prohibitive. In this specific situation of communications systems, using unshielded twisted pair wiring cables is the only practical alternative.
Performance requirements for conductive pathways are set forth in ANSI/TIA/EIA-568-A, (commercial building telecommunications cabling standard). In category 6 draft-addendum in that standard, the minimum acceptable performance values are 54 dB at 100 MHz, 48 dB at 200 MHz and 46 dB at 250 MHz.
Crosstalk generated at the connection between cables and the connectors, particularly plug connectors has become a significant problem. A very significant problem involves the deformation of the cable by the connector strain relief.